The present invention relates to a device for perforating, die-cutting, cutting or creasing at printing machines, comprising a supporting foil provided with strips at two opposite edges to be affixed to the fixing means of a rubber blanket cylinder of a printing unit or to the forme cylinder of a coating unit. The invention relates also to the use of the inventive device for envelope printing or spot varnishing.
A counter-pressure device for effectuating perforations and/or punching at offset sheet printing machines is known from the U.S. Pat. No. 5,623,874 of the same applicant. In that known device it is particularly provided for to replace the rubber blanket by a hard foil which can be mounted by a fixing means to the rubber blanket cylinder of a printing unit or to the forme roller of a coating unit. The use of a hard foil instead of the rubber blanket resulted in a significant improvement with respect to the then known state of the art, particularly by allowing very precise punching and perforating and an increase in the passing rates in perforating. It has, however, proved that the use of such known device is not recommended in endless printing machines.
In the meantime, further investigations have also shown that it would be desirable to enlarge the use of hard foils instead of rubber blankets to other areas than that indicated in said prior art publication, e.g. the sole offset sheet printing machines and to facilitate and render more accurate the mounting of perforating and punching tools.
From the German Publication No. 4,138,278 means for punching, creasing and perforating with offset sheet printing machines is known in which a coating unit can either be used for coating or for punching, creasing or perforating. In that device the circumference of the coating forme roller is equipped with a punching sheet steel and the circumference of the printing cylinder with a counter-punching sheet steel or vice-versa, in such a way that the coating forme roller is equipped with a counter-punching sheet steel and the printing cylinder with one or several punching sheets steel. In that prior art document said device is on one side limited to the use in a coating unit and on the other side neither the punching sheet steel nor the counter-punching sheet steel are described more in detail.
Further, from the German Patent No. 2,341,326 a multicolour offset sheet printing machine is known with means for perforating, in which patent it is noticed that for easier access of the perforation rules they are not to be mounted on the counter-punching cylinder but on the rubber blanket cylinder. They are, however, glued onto the elastic rubber blanket of the rubber blanket cylinder. The use of the interposed elastic rubber blanket may well eliminate certain deficiencies of the perforation rules. It prevents however to achieve precise perforations and slows down considerably the passing rate.
Starting from this prior art it is an object of the present invention to provide for a device for perforating, die-cutting, cutting and creasing which means can be used in offset sheet printing machines as well as in endless printing machines and which means allows a clean and fast operation and can easily and precisely be positioned. It is a further object of the invention to provide for easier and faster envelope printing and spot varnishing.